Copolymer compositions based on vinyl aromatic monomers and vinyl phosphonic acid derivatives are known in the art. For example, Grey et al. (U.S. Pat. Nos. 5,109,033 and 5,116,882) teach how to make polymer beads by an aqueous suspension polymerization process, and to prepare foamed articles similar to polystyrene foam by expanding the beads in a mold with steam. These polymers have pendent phosphonic acid groups when a vinyl phosphonic acid monomer is used.
U.S. Pat. No. 5,310,808, filed Jul. 30, 1992, describes noncellular flame-retardant thermoplastic copolymers based on vinyl phosphonic acid derivatives. These copolymers are grafted onto a rubber such as styrene-butadiene rubber. Chemical incorporation of a sufficient amount of the vinyl phosphonate monomer makes these compositions flame retardant, while grafting onto rubber improves flexibility and impact properties.
A limiting disadvantage of vinyl aromatic/vinyl phosphonic acid copolymers that are not grafted onto rubber is that they can be rather brittle. Other ways of imparting flexibility to these polymers without the need to polymerize in the presence of a rubber would be valuable.
Although numerous useful rubber-toughened styrenic polymers are known (e.g., high-impact polystyrene (HIPS), ABS, and rubber-modified styrene-maleic anhydride copolymers), these polymers are generally opaque, which limits their potential utility in applications such as coatings and clear packaging.
U.S. Pat. No. 5,237,028, filed Dec. 12, 1991, describes compositions useful for absorbing organic liquids. These compositions are reaction products of phosphonic acid group-containing polymeric resins and diamines or polyamines, including low molecular weight diamines and polyamines. Mono-functional amines are not suitable for use.
Amine-terminated polymers are also well known. Examples include amine-terminated polybutadiene and amine-terminated polyethers such as JEFFAMINE polyethers (products of Texaco Chemical Company). These polymers are particularly useful in the polyurethane industry, but have not been used to improve the flexibility of copolymers derived from vinyl aromatic monomers and vinyl phosphonic acids.
Still needed are new ways to make elastomeric, non-brittle copolymers from vinyl aromatic monomers and vinyl phosphonic acid monomers, particularly without the need to copolymerize the vinyl monomers in the presence of a rubber. Also desirable are styrenic polymers that are elastomeric and transparent, which would be useful for clear packaging and coatings.